====================== Astrometry Resources ====================== .. _geo names search facility: http://geonames.nga.mil/ggmagaz/ .. _JPL ephemerides: http://ssd.jpl.nasa.gov/?ephemerides .. _HORIZONS online ephemerides generator: http://ssd.jpl.nasa.gov/?horizons .. _The Astronomical Almanac: http://www.usno.navy.mil/USNO/astronomical-applications/publications/astro-almanac .. _SOFA: http://www.iausofa.org/ .. _SOFA Board: http://www.iausofa.org/board.html .. _IAU Division 1: http://www.iau.org/science/scientific_bodies/divisions/I/ .. _IERS: http://www.iers.org/ .. _USNO Astronomical Applications: http://www.usno.navy.mil/USNO/astronomical-applications/ .. _The Explanatory Supplement to the Astronomical Almanac: http://www.usno.navy.mil/USNO/astronomical-applications/publications/exp-supp .. _USNO Astronomy Information Center: http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/astronomical-information-center .. _USNO Astrometry: http://www.usno.navy.mil/USNO/astrometry .. _USNO Earth Orientation: http://www.usno.navy.mil/USNO/earth-orientation .. _Precise Time: http://www.usno.navy.mil/USNO/time .. currentmodule:: pytpm This section will given some pointers to resources for obtaining data related to astrometry. Links to some documents that describe concepts used in astrometry calculations are also present. While working with data from the sources mentioned below, it is helpful, even critical, to subscribe to mailing lists and newsletters, that announce important updates. This applies to code libraries as well as data sources. `The Astronomical Almanac`_ is a collection of information on most of the topics listed below. `USNO Astronomical Applications`_ division maintains a large repository of information on astronomical phenomena and astrometric data. .. _delta_at_info: Time scales and calendars ========================= Information on ``delta_AT = TAI - UTC``, leap seconds in UTC and other similar information are available from the International Earth Rotation and Reference Systems Service (IERS). See the section on :ref:`iers_sec` below. Information on ``delta_AT`` also maintained in the file ftp://maia.usno.navy.mil/ser7/tai-utc.dat, which lists ``delta_AT`` values beginning from 1961 Jan. 1. See files in the directory ftp://hpiers.obspm.fr/eop-pc/eop/eopc04_05 for listings that give ``delta_UT = UT1 - UTC`` values. The last two resource are the easiest way for obtaining ``delta_AT`` and ``delta_UT``, respectively. PyTPM has a function :func:`pytpm.tpm.delta_AT` that gives the value for ``delta_AT`` for the given ``UTC``. But this file has to be updated, using values in the ``tai-utc.dat`` file mentioned above. Notification of changes are notified through the IERS mailing lists. See :ref:`iers_sec` below. Geographical and Earth data =========================== Use the `geo names search facility`_ provided by the `National Geospatial-Intelligence Survey `_ for finding longitude and latitudes of places, using place and country names. Google Maps and Google Earth also give longitude, latitude and altitude information. Websites of individual observatories may have information on their geodetic and geocentric positions. Use the information in section on :ref:`iers_sec` for data on polar motion and other Earth orientation parameters. Ephemerides =========== Positions and orbital elements of astronomical objects and Earth satellites, including Earth-Sun ephemerides. + `IAU Minor Planet Center `_ Definitive collection of information on minor planets, including orbital elements. + `The Asteroid Orbital Elements Database `_ By Edward Bowell, based on astrometric observations downloaded from the Minor Planet Center and "updated daily". + `JPL ephemerides`_ and `HORIZONS online ephemerides generator`_ JPL planetary ephemerides can be downloaded from the `JPL ephemerides`_ site. HORIZONS is an online system for generating custom ephemerides. Output can be generated in the form of osculating elements as well as in the form of Cartesian vectors (position, velocity and acceleration). Ephemerides for more than 60 satellites are also available. + `Mars ephemerides generator `_ + `USNO astrometry service `_ Data on solar system objects observed with the Flagstaff Astrometric Scanning Transit Telescope is available at http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/solsys. + Earth satellites NORAD elements can be obtained from `CelesTrak `_. `NASA space flight center `_ has orbital elements for ISS. Constants and fundamental data ============================== .. _Physical Measurements Laboratory at NIST: http://www.nist.gov/physlab/ .. _Physical Reference Data: http://www.nist.gov/pml/data/index.cfm .. _CODATA: http://physics.nist.gov/cuu/Constants/index.html Fundamental physical data, constants and physical properties of astronomical objects. + Physical data and fundamental constants. + `CODATA`_ at National Institute of Standards and Technology (NIST). Internationally recommended values of the fundamental physical data. + `Physical Measurements Laboratory at NIST`_, especially the `Physical Reference Data`_ section. + Data for solar system objects `JPL solar system dynamics `_. + IAU Working Group on Numerical Standards for Fundamental Astronomy IAU/IERS approved physical and astronomical constants. NSFA website: http://maia.usno.navy.mil/NSFA.html. Astrometry libraries and applications ===================================== Examples of software similar to TPM and PyTPM. Some of these can be used to calculate quantities such as rising and setting time for Sun and Moon, phases of Moon and others. .. _SLALIB: http://www.starlink.rl.ac.uk/star/docs/sun67.htx/sun67.html .. _NOVAS: http://www.usno.navy.mil/USNO/astronomical-applications/software-products/novas .. _XEphem: http://www.clearskyinstitute.com/xephem/ .. _PyEphem: http://rhodesmill.org/pyephem/ .. _Kapteyn: http://www.astro.rug.nl/software/kapteyn/ .. _iraf.images.imcoords.skyctrans: http://stsdas.stsci.edu/cgi-bin/gethelp.cgi?skyctran .. _JSky: http://archive.eso.org/cms/tools-documentation/jsky/ .. _JSkyCalc: http://www.dartmouth.edu/~physics/faculty/skycalc/flyer.html .. _SkyCalc: http://www.dartmouth.edu/~physics/people/faculty/thorstensen.html .. _Astronomy on the Personal Computer: http://www.amazon.com/Astronomy-Personal-Computer-Oliver-Montenbruck/dp/3540672214 .. _Practical Astronomy With Your Calculator: http://www.amazon.com/Practical-Astronomy-Calculator-Peter-Duffett-Smith/dp/0521356997 + SLALIB_ + SOFA_ + NOVAS_ + XEphem_ and PyEphem_ + Kapteyn_ + `iraf.images.imcoords.skyctrans`_ + JSky_ + JSkyCalc_ and SkyCalc_ + `Astronomy on the Personal Computer`_ + `Practical Astronomy With Your Calculator`_ Sky visualization and exploration ================================= + http://www.sky-map.org/ + http://skymaps.com/ + http://www.google.com/sky + http://www.worldwidetelescope.org (Web based but only for Win and Mac) + http://skyview.gsfc.nasa.gov/ + `Stellarium with VirGO `_ + `ALADIN `_ + XEphem_ + JSkyCalc_ Catalogs ======== Astrometry catalogs i.e., catalogs of accurate positions and proper motion ; data can be accessed using the `ViZier service `_. .. _Hipparcos: http://www.rssd.esa.int/index.php?project=HIPPARCOS&page=Overview .. _USNO B 1.0: http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/usno-b1.0 .. _NOMAD: http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/nomad + Hipparcos_ + `USNO B 1.0`_ USNO-B1.0 is the latest catalog from the USNO Precision Measuring Machine project. It contains over 1,000,000,000 entries and provides positions, magnitudes, and proper motions for each object. + `PPMXL Catalog `_ A new determination of mean positions and proper motions on the ICRS system by combining USNO-B1.0 and 2MASS astrometry. + NOMAD_ (Naval Observatory Merged Astrometric Dataset) NOMAD is a simple merge of data from the Hipparcos, Tycho-2, UCAC-2 and USNO-B1 catalogs, supplemented by photometric information from the 2MASS final release point source catalog. The primary aim of NOMAD is to help users retrieve the best currently available astrometric data for any star in the sky by providing these data in one place. Documents and papers ==================== These documents explain concepts such as precession, nutation, time scales and others related to astrometry. The various papers mentioned in these documents are also important sources of information on astrometry related concepts. + `The Explanatory Supplement to the Astronomical Almanac`_ + NOVAS_ Manual + :download:`TPM Manual ` + SLALIB_ Manual + `SOFA Documents `_ + SOFA Manual. + SOFA Tools for Earth Attitude. + SOFA Time Scales and Calendar Tools. + `Astronomy on the Personal Computer`_ This books is essentially a reference manual for the C++ software that is distributed with it. It has good explanations of concepts such as orbital elements, precession angles and others. + `Practical Astronomy With Your Calculator`_ Step-by-step instructions on performing astrometry calculations using a calculator. Great book for understanding basic ideas in astrometry. The SOFA cookbooks, Tools for Earth Attitude and Time Scales and Calendar Tools, are perhaps the best documents to start with. `Spherical Astronomy`_ by Robin M. Green and `Fundamentals of Astrometry`_ by Jean Kovalevsky and P. Kenneth Seidelmann, are two relevant textbooks. .. _Spherical Astronomy: http://www.amazon.com/Spherical-Astronomy-Robin-M-Green/dp/0521317797 .. _Fundamentals of Astrometry: http://www.amazon.com/Fundamentals-Astrometry-Jean-Kovalevsky/dp/0521642167 Organizations ============= USNO ---- - `USNO Astronomical Applications`_ Services such as date calculations, setting and rising time and others. Information on astronomical concepts behind the above calculations are also provided. - `USNO Astrometry`_ Links to astrometric catalogs such as NOMAD, UCAC, USNO-B1.0 etc., . Observations of planetary satellites and minor planets are also provided. - `USNO Earth Orientation`_ USNO is the International Earth Rotation and Reference Systems Service (IERS) Rapid Service/Prediction Center (RS/PC) for Earth Orientation. Most of the information in IERS bulletins are issued from USNO. - `Precise Time`_ Information on obtaining precise time (UTC). JPL Solar System Dynamics ------------------------- `JPL SSD `_ collects information on orbits, ephemerides and physical characteristics of solar system objects. Standards Of Fundamental Astronomy ---------------------------------- SOFA_, or the `SOFA Board`_, is responsible for implementing the definitive algorithms for standard models used in Astronomy. This organization works under `IAU Division 1`_. Implementations of the algorithms in Fortran 77 and ANSI C are made available by SOFA. SOFA has an `email service `_ that sends notifications of software releases and other information. .. _iers_sec: International Earth Rotation and Reference Systems Service ---------------------------------------------------------- IERS_ is responsible for defining and determining Earth orientation, International Terrestrial Reference System/Frame, International Celestial Reference System/Frame and geophysical fluids data. IERS also provides information on leap seconds and DUT1, which are related to Earth orientation. It was established by the IAU and the International Union of Geodesy and Geophysics. IERS has an `email notification service `_ that delivers all their data bulletins and messages: + Bulletin A (weekly) IERS Bulletin A contains Earth orientation parameters x/y pole, ``UT1 - UTC`` and their errors at daily intervals and predictions for 1 year into the future. But also see files in the directory ftp://hpiers.obspm.fr/eop-pc/eop/eopc04_05 for listings that give ``UT1 - UTC`` values. These are probably easier to use. For example the file ``eopc04_IAU2000.62-now`` in the above directory gives ``UT1 - UTC`` values, in addition to many others, for the appropriate period. + Bulletin B (monthly) IERS Bulletin B provides current information on the Earth's orientation in the IERS Reference System. This includes Universal Time, coordinates of the terrestrial pole, and celestial pole offsets. + Bulletin C (bi-annual) Announcement of leap seconds in UTC and information on ``UTC-TAI``. + Bulletin D (irregular) Announcements of the value of ``DUT1 = UT1 - UTC`` to be transmitted with time signals with a precision of ±0.1s. + Messages (irregular) The IERS Messages contain short and rapid information about the IERS and its products for contributors and users. See `IERS data products page `_ page for all data provided by IERS. The "directory" http://maia.usno.navy.mil/ser7/ contains collection of files that has data from all published bulletins, for example bulletin B. For information of the contents of various bulletins see appropriate files in ftp://hpiers.obspm.fr/iers/bul. See files in the directory ftp://hpiers.obspm.fr/eop-pc/eop/eopc04_05 for listings that give ``UT1 - UTC`` and other Earth orientation parameters.